1. Field of Invention
The present invention is directed to a scanning system and image processing system and methods thereof for stitching together overlapped image data. More specifically the present invention is directed to such systems and methods that produce such overlapped image data from a plurality of overlapped sensors and stitch the overlapped image data together.
2. Description of Related Art
Modem fall-width scanning systems typically use a system where a document to be scanned is stationary and the scanning system moves. A single mobile carriage is typically utilized to scan the entire document. The carriage system, conventionally, includes a fall-width sensor array system and a light source. The sensor array system may be a CCD array that receives light reflected from the document and converts the light into electrical signals representing the intensity of the received light. The electrical signals are then passed on to an electronic subsystem which typically includes a controller that performs the necessary image processing operations to prepare the image data either for display on display devices such as a CRT, for storage on a storage device, or for recording or printing on a medium such as a document, if the system is part of a copier.
Another example of a scanning system is a constant velocity transport (CVT) scanning system where the document moves and the scanning system is stationary. In the CVT scanning system, a single stationary scanning system is utilized to scan the entire document, wherein the document is moved past the scanning system. This type of scanning system, conventionally, includes a full-width CCD sensor array system and a light source. As in the fall-width scanning system described above, a CVT scanning system has the full-width CCD sensor array receive light reflected from the document and it converts the light into electrical signals representing the intensity of the received light. Electrical signals are then passed on to an electronic subsystem controller which performs the necessary image processing operation so as to prepare the image data either for display, storage or recording as described above.
Conventional scanning systems may utilize multiple sensors, or sensor arrays, to create a full-width scanning system. Typically, such a scanning system may include a plurality of sensors that are overlapped with each other, to provide a fall-width scan. These types of scanning systems have typically switched from one sensor to the next in the middle of the scanned line. However, because the individual pixels are very small, the pixels in the overlapping regions of the sensors are typically not precisely aligned from one sensor to the next. This pixel separation causes image defects, which are especially evident for halftone patterns in an original document that straddles the region where the sensors are overlapped and the system will switch from one sensor to another.
The conventional scanning systems have stitching circuits that typically simply switch from a first sensor (or channel) to a second sensor at some point in the overlapped region. For example, U.S. Pat. No. 5,532,845, assigned to the same assignee as the present application, and which is incorporated herein by reference in its entirety, discloses a digital scanner that includes a stitching circuit for putting two channels of image data together. This stitching circuit switches from the first channel to the second channel when it processes the overlapped scan lines using conventional stitching methods. This system does not account for a misalignment of pixels from by one sensor to the next in the overlapped region.
One aspect of the present invention is a multi-sensor scanning system or image processing system which includes a plurality of sensors each scanning a portion of a document to produce image data. Each of the sensors overlap adjacent sensors and the sensors thus produce overlapped image data. The image data is stitched together to form a complete image by performing a weighted averaging over the overlapped image data. The weighted averaging may be linear or non-linear.
Another aspect of the present invention is a scanning system or image processing system that includes a plurality of sensors, with each of the sensors scanning a portion of the document to produce image data. Each of the sensors overlap adjacent sensors so that the image data includes overlapped image data. The image data from the sensors is stitched together to form a compete image by varying a stitch location within the overlapped image data. A stitch location may be varied from scanline to scanline in the slowscan direction.
A more complete understanding of the present invention can be obtained by considering the following detailed description in conjunction with the accompanying drawings, wherein like index numerals indicate like parts.